1. Field of the Invention
The invention relates to air-charge cooling and heating devices used in the induction circuits of internal combustion engines and more particularly to those types of engines which employ mechanically driven superchargers or hot gas driven turbochargers, hereinafter simply referred to as superchargers.
The invention serves the same purpose as those devices referred to in the art as "inner-coolers" or, "after-coolers", which are most prevelently used in the design of high performance engines. However, unlike the latter devices, cooling in the air temperature classifier hereinafter called the "classifier", is achieved entirely within the charge air stream by the principle of conservation of angular momentum and therefore does not require convective or conductive heat transfer to an outside cooling media.
The invention also relates to fuel heating devices used in aircraft engine carburetor de-icers necessary for high altitude flight and to automobile engine air preheaters necessary for the prevention of unburned hydrocarbon pollution during startup. In both applications combustion is improved through the reduction of fuel droplet size by vaporization which is more efficient at the higher temperatures.
Specifically the air temperature classifier makes use of those heating and cooling processes which operate on the established principle of sensible heat differences measured as temperature gradients within atomic, unimolecular, or homogeneous mixtures of gases rapidly moving in counterflowing vortices within a single chamber. These devices are commonly referred to in the art as "vortex coolers", or "vortex heaters", depending on the manner of their application.
The invention operates on the principle of conservation of angular momentum and though similar in appearance should not be referenced to gas-solid or gas-liquid cyclone separators which are used to affect a separation of material of different physical state based on the principle of centrifugal mass distribution within a single outer vortex which is a completely different principle of operation.
2. Description of Prior Art
The principle of the "hot-cold" tube as it is often referred to, or the "Maxwell demon", named after its discoverer, has been studied since the middle of the nineteenth century. More recent studies by Ranque in France in the early 1930's and even more recently by Hilsch in Germany in the mid 1940's have brought the design to a point of practical application. However, the specific principle has never been applied to engine induction and exhaust processes except as a means of centrifugal separation of material substances of different physical state.
The manner of generating the vortex flow in the invention presented is different from all other known designs. In all previous designs of vortex temperature generating equipment, the inlet flow to the chamber has been introduced tangentially to the cylindrical surface in a direction which is perpendicular to the longitudinal axis of the chamber. The flow of the vortex toward the opposite end of the chamber is therefore caused by pressure differences between the inlet and outlet of this type of design construction. In the design presented the inlet flow is also introduced tangentially to the cylindrical surface but unlike previous devices the flow is directed in a more or less axial direction relative to the longitudinal axis of the chamber. This is done primarily to overcome the marginal discharge pressure conditions of most supercharger compressors relative to their ability to produce the pressure and velocity requirements within the vortex chamber necessary to generate a sensible temperature difference between the two outlet streams. By introducing the flow axially to the chamber and inlet manifold, and causing it to swirl while it moves in this direction, increases the velocity head at the inlet of the vortex generating orifices providing axial stream momentum to the vortex within the chamber causing it to more rapidly traverse the length of the chamber rather than depending on pressure differences alone as is the case of all other vortex equipment. This increases the relative velocity between the inner and outer counterflowing vortices formed by this type of equipment and thereby decreases the equilibruim heat transfer across the interface by shortening the period of contact thereby increasing the sensible heat difference between each vortex stream exiting the chamber. In the automotive engine applications, vortex phenomena was first applid by Bauer in 1965 in his U.S. Pat. No. 3,426,513, "Vehicular Vortex Cyclone Type Air and Gas Purifying Device", and in 1968 by Fiore in his U.S. Pat. No. 3,566,610, "Method and Apparatus For Separating Fluids". In both of these previous applications the principle of operation depends on the relationship between the curvilinear acceleration and the resulting radial mass distribution of solid impurities within the vortices, which are used as separator devices rather than temperature classifiers as claimed in the present invention.
Unlike previous vortex applications in the engine field, the present invention is not used as a centrifugal separator for cleaning the induction air or to rid the exhaust gas stream of solid particulate matter. Air entering the induction manifold of the temperature classifier is presumed to be first filtered through a porous or fibrous media or by other methods commonly in use. It should also be noted that the invention presented in its present form is not intended or suitable for application in the engine exhaust stream.
The invention is designed for use in the induction manifolds of super-charged internal combustion engines as a temperature management device. Management of the inlet temperature provides a means of controlling preignition in gasoline engines and can also be used to extend the lean limit operating range of most engines. Combustion and volumetric efficiencies can also be improved by systematic classification and management of the inlet stream temperature.
Engines which run on gasoline and employ electrical spark or other types of electrically timed ignition are sensitive to air charge temperature because of both preignition and detonation limits. In this regard the octane requirements for an engine operating at a given compression ratio can be substantially reduced by the air temperature classifier by cooling the charge entering the chamber. Anomalies originating in the combustion chamber, such as the tendency to develope hot spots on clearance surfaces, which ignite the charge before electrically induced ignition are also reduced by cooling the air.
The air temperature classifier can also be used to improve the performance of engines by cooling the charging air. The cooler air charge entering the engine permits a larger induction by weight which significantly increases the volumetric efficiency. Cooling in this manner can produce 5 to 10 percent more power at the same speed as the uncooled system operating at a higher manifold pressure.
Looking now at the method of applying the warm air outlet of the classifier for improving the combustion efficiency and extending the lean operating limits of the engine. The lean limit operating range of the engine can be extended by improving fuel-air distribution within the intake manifold adjacent to the engine inlet. Improved air fuel distribution is best achieved by the use of fuel atomizing devices that will produce droplet sizes approaching 10 to 30 microns. This type of operation is most easily achieved by diverting the hot air stream from the air temperature classifier to the atomizer such that vaporization further reduces the size of the atomized droplets. Previous investigators have used the elevated temperature of the exhaust manifold or water jacket of the engine for this purpose while others have used electrical heating devices. Because vaporization is a cooling process the fuel-air charge leaving the fuel atomizing zone is slightly cooler than the charge air from the classifier entering the zone. The fuel-air mixture is reunited with the cold air component of the classifier at a point downstream of the atomizing zone. Maintaining the fuel-air charge mixture above the system dew point is achieved by controlling the fuel-air mixture ratio above the corresponding saturation point at the engine inlet temperature.
Operating the engine under lean limit conditions results in worthwhile reduction of exhaust emissions and very significantly reduces the fuel consumption rate.
The air temperature classifier, as is the case of most vortex chambers, is a simple flow device capable of separating compressed gaseous fluids into two outlet streams of different temperature. The temperature difference between the outlet streams increases with inlet velocity, which for best results should be sonic. This is achieved by increasing the discharge pressure from the supercharger compressor to a value approximately 21/2 times the internal pressure of the classifier chamber which is maintained at about 16 to 17 pounds of absolute pressure at the engine maximum load conditions. Inlet pressures of this magnitude can be supplied by most supercharger compressors at slightly above midrange operation. At lower boost pressures, during partial load operation of the engine, the backpressure on the classifier exit orifices (outlets) are reduced by throttling the amount of air entering the inlet of the classifier, thus maintaining the uninterrupted sonic flow to the classifer for longer periods of time.
As an alternate application of the invention, the classifier air stream may be directed to side-ports in the engine cylinder and thereby supply cooling air to the piston crowns. The cool air stream would be supplied to manifolding similar to that taught by the McWhorter U.S. Pat. Nos. 4,108,119, 4,248,199 and 4,312,313. Operation in this manner decreases the temperature of air entering the engine cylinder at this point and thereby provides more effective cooling of the piston crowns and is by its nature more specifically applicable to those systems which utilize stratified charging techniques.